Soil sensor assembly

ABSTRACT

A soil sensor assembly and methods of measuring undisturbed soil are disclosed. The soil sensor assembly can be a volumetric water content (VWC) sensor. The soil sensor assembly can include at least one soil probe. The soil probes can be secured to a support to enable an installation of the soil sensor assembly in a target soil. The soil probes can include helical blades secured concentrically along the support at predefined longitudinal locations. The soil probes can include at least one radiofrequency (RF) electrode secured to the helical blades at a predefined radial distance from a longitudinal axis of the support. The soil sensor assembly can also include at least one electronics unit coupled to the RF electrodes to receive and/or transmit RF signals from the RF electrodes. The soil sensor assembly can enable a self-tapping installation action and/or enable alienating the soil measurements (e.g., by RF electrodes) away from a disturbed soil.

RELATED APPLICATIONS

This application is a national phase filing under 35 USC 371 ofInternational Application No. PCT/IL2016/000022, filed on Dec. 1, 2016,which claims priority of U.S. Patent Application No. 62/262,670, filedDec. 3, 2015, and U.S. Patent Application No. 62/339,970, filed May 23,2016, the entirety of which are incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention discloses a rotatably anchorable soil sensor,which provides an easy means of unbiased measuring of undisturbed soil.

2. Discussion of Related Art

Current volumetric water content (VWC) profile sensors can include apole and/or circular radiofrequency (RF) electrodes wrapped around thepole. Typically, current VWC sensors can significantly disturb a targetsoil during an installation and/or can require pre-drilling proceduresin order to be installed. Unmatched pre-drilling and VWC sensor'sdimensions can result in a poor contact between the VWC sensor and thesoil. The poor contact between the moisture sensor and the soil and/ordisturbed soil can introduce measurement errors. For example, a gap canbe generated between the VWC sensor and the soil, in which verticalwater flow and/or accommodation can occur, thereby affecting the VWCmeasurement of the target soil. Moreover, the pre-drilling requirementcan increase the installation costs.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a soil sensor assemblyincluding: a rotatably anchorable portion to be rotatably anchored in asoil; at least one soil sensor mounted onto the rotatably anchorableportion; and a communicator for communicating at least one output of theat least one soil sensor to a location remote from the at least one soilsensor assembly.

Another aspect of the present invention provides a volumetric watercontent (VWC) sensor including: a support to enable installation of theVWC sensor in a target soil; at least one VWC probe positioned at apredefined longitudinal location along the support, the at least one VWCprobe including: a helical blade secured along its inner lateral side toan outer surface of the support, and at least one radiofrequency (RF)electrode secured to the helical blade at a predefined radial distancefrom the support; and at least one electronics unit coupled to the atleast one RF electrode to transmit and receive RF signals from the atleast one RF electrode.

Another aspect of the present invention provides a volumetric watercontent (VWC) sensor comprising: at least one VWC probe including atleast two radiofrequency (RF) electrodes, the at least one VWC probe tomeasure a VWC of a target soil in a measurement region between the atleast two RF electrodes, and a support to secure positioning of the atone VWC probe, wherein the support occupies less than 10% of themeasurement region.

These, additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows;possibly inferable from the detailed description; and/or learnable bypractice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the invention and to showhow the same may be carried into effect, reference will now be made,purely by way of example, to the accompanying drawings in which likenumerals designate corresponding elements or sections throughout.

In the accompanying drawings:

FIG. 1A is an illustration of a rotatably anchorable sensor and itsundisturbed soil installation, according to some embodiments of theinvention (on a left-hand side of FIG. 1A) and current soil sensors andinstallation methods of slurry installation of a profiling sensor, duginstallation of scientific sensors and trench installation of scientificsensor, according to the prior art.

FIGS. 1B-1C are illustrations of a volumetric water content (VWC)sensor, according to some embodiments of the invention;

FIGS. 2A-2E are illustrations of disassembled volumetric water content(VWC) sensor, according to some embodiments of the invention;

FIGS. 3A-3B are illustrations of various configurations of a tip ofvolumetric water content (VWC) sensor, according to some embodiments ofthe invention;

FIGS. 4A-4D are illustrations of various configurations ofradiofrequency (RF) electrodes of a volumetric water content (VWC)sensor, according to some embodiments of the invention;

FIGS. 5A-5E are illustrations of a volumetric water content (VWC) sensorincluding radiofrequency (RF) electrodes protruding above at least onesurface of helical blades, according to some embodiments of theinvention.

FIG. 6 is an illustration of configuration of volumetric water content(VWC) sensor with a support being a coreless helical blade, according tosome embodiments of the invention;

FIG. 7 is an illustration of a volumetric water content (VWC) probeincluding segmented RF electrodes, according to some embodiments of theinvention;

FIG. 8 is a schematic block diagram illustrating an electronics unit ofvolumetric water content (VWC) sensor, according to some embodiments ofthe invention;

FIG. 9 is a schematic block diagram of an electronic circuitry ofelectronics unit of volumetric water content (VCW) sensor, according tosome embodiments of the invention;

FIG. 10 is a flowchart illustrating a method of measuring a undisturbedvolumetric water content (VCW), according to some embodiments of theinvention;

FIG. 11 is a flowchart illustrating a method of installing a soil sensorassembly, according to some embodiments of the invention;

FIG. 12A is a graph illustrating volumetric water content (VWC)measurement results being measured by a prior art profile sensor,according to the prior art; and

FIG. 12B is a graph illustrating volumetric water content (VWC)measurement results being measured by a VWC sensor, according to someembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Effective agriculture can depend on obtaining accurate, continuous,in-field soil measurements, for example soil moisture measurements,including soil measurements at different sub-surface depths. A targetsoil can be not uniform and therefore continuous measurements can berequired to be measured at multiple locations in a field to best informagricultural actions. For example, different parts of the field canrequire different amounts of irrigation, which can require continuoussoil-moisture monitoring at different specific locations in the field.Current soil sensor devices can invariably provide biased measurementsof sub-soil due to the disturbance of the soil, caused by, for example,their installation. Current scientific installation procedures that canprovide, for example, unbiased measurements, can be complex andimpractical in a working agricultural field. Current soil sensor devicesdo not provide practical, accurate, continuous and/or in-field soilmeasurements of sub-surface soil. The present invention describes a soilsensor device, which can provide continuous, unbiased measurement ofun-disturbed sub-surface soil, and/or can include a simpledo-it-yourself installation.

FIG. 1A presents a rotatably anchorable sensor 100 and its undisturbedsoil installation 105, according to some embodiments of the invention(on a left-hand side of FIG. 1A) and current soil sensors andinstallation methods of slurry installation 50 of a profiling sensor,dug installation 40 of scientific sensors and trench installation 30 ofscientific sensor, according to the prior art.

Slurry installation 50 can typically include drilling a wide-borevertical hole, preparing slurry by mixing the soil from the hole withwater, pouring the slurry back into the hole, and/or placing apole-shaped profiling sensor 51 into the into slurry-filled verticalhole. The profiling sensor 51 can be therefore in contact with slurry52, ensuring close contact of top sensor 53 and bottom sensor 54 withthe slurried soil. One disadvantage of slurry installation can be thatslurry 52 is a disturbed soil medium, which can enhance a vertical flow59 of water through the slurry 52, thereby biasing the measurements ofthe sensors 55, 54. For example, measurements of bottom sensor 54 can beprone to reflect soil moisture that can be actually that of top soil dueto, for example, excessive vertical flow 59 of water, through the slurry52. Typically, following an irrigation event, measurements from thebottom sensor 54 can erroneously show a rise in soil moisture that canbe similar in timing and amplitude, to measurements of the top sensor55. Such measurements can be biased, since water takes time to filtratedown through undisturbed soil, as is well known in the art.

Dug installation can include a vertical hole being dug, through whichthe sensors, e.g., top scientific sensor 41 and bottom scientific sensor42, can be placed at different desired depths, such that their sensingpart, e.g., prongs, are pierced into the wall of the hole to measureintact soil. The sensors 41 and 42 can be typically connected by wire toa logger 45 on the ground, and the hole is then filled with soil-fill43. One disadvantage of dug installation method can include disturbedsoil-fill 43, through which a vertical flow 49 of water can occur.Thereby, bottom scientific sensor 42 can give erroneous measurementsthat correspond in timing and amplitude to those of top scientificsensor 41, reflecting unnaturally excessive vertical flow 49 of waterthrough the soil fill 43. Another disadvantage of dug installation 40can include difficult and time-consuming installation.

Trench installation 30 can provide a scientifically robust method forinstalling scientific sensors 31. One disadvantage of the trenchinstallation can include impractical implementation in an activeagricultural field. In this method, a deep trench, Trench installationcan typically include drilling one yard deep and wide, dug and/or widebore (e.g., 60 cm) vertical peers into a wall of the trench at thedesired depths, and/or manually placing scientific sensors through thevertical peers, and/or piercing their sensing prongs into undisturbedsoil at the far end of the peer, at an upward angle of 45 degrees, sothat no seepage of water through the peer to affect the sensor prongscan occur. The trench can be covered with a tarp, to preventaccumulating water to enter the peers, and/or accumulated water to bepumped from the tarp covered trench. Trench installation 30 can avoidbias of disturbed soil and vertical flow, however—it can be utterlyimpractical in the setting of an agricultural field. more so whenmultiple measurements are needed from different parts of a field.

Currently available soil sensor devices can provide biased measurements,due to measuring disturbed soil, and/or due to biased vertical waterflow. While the description above is of soil moisture measurements, thesame can be true for other measurements that can include soil nutrients,micro nutrients, genetic measurements, organic compounds, and many othermeasurements.

The present invention discloses a rotatably anchorable spiral sensor100, which can be installed into sub-surface soil 105, and/or provideunbiased, measurements from undisturbed soil. The disclosed spiralsensor 100 can include sensors 120 at multiple depths, such as a topsensor 120 a located on, or integrated into a helical blade 122 a,and/or a sensor 120 b located on or integrated helical blade 122 b.Spiral sensor 100 can be installed by rotating it into the subsurfacesoil 105, and so both helical blades 122 a, 122 b can be cut into thesubsurface soil, thereby placing sensors 120 a, 120 b in direct contactwith undisturbed soil, and providing unbiased measurements from thesoil, measurements that are not subject to excessive vertical waterflow. Installation of spiral sensor 100 does not require slurry and/orsoil-fill, thereby no biased measurements due to vertical flow canoccur. Sensors 120 a, 120 b can include helical blades 122 a, 122 b awayfrom shaft 110 of the spiral sensor 100, thereby minimizing possiblevertical flow along shaft 110 to bias the readings of the sensor. Insome embodiments, a shape of electronics bay 130 of the spiral sensorand/or the shape of helical blades 122 a, 122 b can minimize verticalflow.

Spiral sensor 100 can provide accurate soil measurements of undisturbedsoil and/or provide measurement that are not unbiased by artifactualvertical flow.

Advantageously, disclosed spiral sensor(s) 100 provide high qualityresults without disturbing the soil. In some embodiments, spiralsensor(s) 100 may be installed in a simple manner and using five to tenfold shorter installation time with respect to the prior art, forexample in the order of magnitude of minutes or tens of minutes insteadof hours. Advantageously, in some embodiments, disclosed spiralsensor(s) 100 may revolutionize the domain of soil sensors, offering forthe first time, a device that provides continuous, accurate, soilmeasurements of undisturbed soil, unbiased by inadvertent vertical waterflow, and with an unprecedented simplicity and speed of a trulydo-it-yourself installation.

A soil sensor assembly and methods of measuring undisturbed soil aredisclosed. The soil sensor assembly can be a volumetric water content(VWC) sensor. The soil sensor assembly can include at least one soilprobe. The soil probes can be secured to a support to enable aninstallation of the soil sensor assembly in a target soil. The soilprobes can include helical blades secured concentrically along thesupport at predefined longitudinal locations. The soil probes caninclude at least one radiofrequency (RF) electrode secured to thehelical blades at a predefined radial distance from a longitudinal axisof the support. The soil sensor assembly can also include at least oneelectronics unit coupled to the RF electrodes to receive and/or transmitRF signals from the RF electrodes. The soil sensor assembly can enable aself-tapping installation action and/or enable alienating the soilmeasurements (e.g., by RF electrodes) away from a disturbed soil. Thesoil sensor assembly can enable measuring properties of undisturbed soiland/or eliminate a vertical water flow along the sensor thereof.

FIGS. 1B-1C are illustrations of a volumetric water content (VWC) sensor100, according to some embodiments of the invention. VWC sensor 100 caninclude a support 110. In some embodiments, support 110 is a rotatablyanchorabable portion. In some embodiments, support 110 can be a pole(e.g., as illustrated in FIGS. 1B-1C). In some embodiments, pole 110 isa monolith having a tapered nail-like shape and/or includes a tip 112.Tip 112 can have a tapered shape that can enable initial penetration ofVWC sensor 100 into a target soil during an installation process.

VWC sensor 100 can include at least one VWC probe 120 secured to anouter surface of pole 110 at predefined longitudinal location along thepole. In some embodiments, VWC sensor 100 includes single VWC probe 120,as shown in FIG. 1B. In some embodiments, VWC sensor 100 includes twoVWC probes 120 a, 120 b separated by a longitudinal distance 152 (e.g.,as shown in FIG. 1B, FIG. 2D) that enable measuring VWC of a target soilat two depths (e.g., profile VWC sensor). In some embodiments, VWCsensor 100 also includes at least one additional soil sensor, forexample, a temperature sensor, a pH sensor, a pressure sensor, asalinity sensor and/or sensor for determining level of minerals in atarget soil.

In some embodiments, each of VWC probes 120 (e.g., each of VWC probes120 a, 120 b as shown in FIG. 1B) includes a helical blade 122 securedalong an inner lateral side to an outer surface of pole 110. Helicalblade 122 can complete a helical path of at least 360° around pole 110.In some embodiments, helical blade 122 can complete 720° around pole110. A shape of helical blade 122 can enable performing a screwingmotion of VWC sensor 100 within a target soil during an installationprocess.

VWC probe 120 (e.g., each of VWC probes 120 a, 120 b as shown in FIG.1B) can include radiofrequency (RF) electrodes 124 secured to helicalblade 122 at a predefined radial distance 154 from pole 110 (e.g., asshown in FIG. 2E). RF electrodes 124 can have a helical shape thatcorresponds to shape of helical blade 122 and/or can complete a helicalpath of at least 360° around pole 110. RF electrodes 124 can be surfaceelectrodes and/or can be secured to at least one of surfaces of helicalblade 122. In some embodiments, RF electrodes 124 can be embedded withinhelical blade 122. RF electrodes 124 can cover at least a portion of thesurfaces thereof. An RF field can be generated by adjacent RF electrodes124 to measure a VWC of a target soil in a measurement region betweenthe adjacent RF electrodes. In some embodiments, helical blade 122 is aRF electrode.

Radial distance 154 can be predefined based on a desired RF field to begenerated by RF electrodes 124 and/or to alienate RF electrodes 124 frompole 110 and/or from a disturbed target soil. In some embodiments, RFelectrodes 124 are positioned at 30% most lateral portion of helicalblades 122.

During a screwing motion of an installation process, helical blade 122 bof VWC probe 120 b enters an undisturbed target soil, thereby providinga good contact between helical blade 122 b and/or RF electrodes 124 band the target soil. Longitudinal distance 152 between helical blades122 a, 122 b and/or diameters of helical blades 122 a, 122 b can bepredefined to, for example, optimize the accuracy of VWC measurement ofthe target soil and/or to provide a good contact between helical blade122 a and/or RF electrodes 124 a and the target soil. For example, adiameter of helical blade 122 a can be greater than a diameter ofhelical blade 122 b (e.g., as shown in FIG. 1B) such that helical blade122 a, which can follow a screwing path of helical blade 122 b duringthe screwing motion of the installation process, enters a undisturbedsoil, thereby providing a good contact between helical blade 122 aand/or RF electrodes 124 a and a target soil.

VWC sensor 100 can include at least one electronics unit (e.g.,electronics unit 160 as shown in FIGS. 8-9) that can transmit and/orreceive RF signals from RF electrodes 124. In some embodiments, at leastone of the electronics units is embedded within pole 110. In someembodiments, at least one of the electronics units is embedded withinhelical blade 122 of at least one of VWC probes 120. In someembodiments, VWC sensor 100 includes an electronics bay 130 secured topole 110 at the end being opposite to tip 112. Electronics bay 130 caninclude at least one of the electronics units. RF electrodes 124 of VWCprobe 120 can be connected to the electronic units and/or to electronicsbay 130 using wiring and/or wireless connections (not shown). In someembodiments, electronics bay 130 includes an antenna 132. In someembodiments, electronics units and/or electronics bay 130 include awireless communications device (e.g., wireless communicator) that canenable transmitting the received RF signals (e.g., by antenna 132) to aremote control station 70. The wireless communications device can be anywireless communications device as is known in the art.

FIGS. 2A-2C are illustrations of disassembled volumetric water content(VWC) sensor 100, according to some embodiments of the invention. FIGS.2D-2E are illustrations of assembled VWC sensor 100, according to someembodiments of the invention. FIGS. 2A, 2C, 2D provide a side view andFIGS. 2B, 2E provide an isometric view of VWC sensor 100.

In some embodiments, pole 110 of VWC sensor 100 includes a first tubularsection 114, a second tubular section 116 and/or a third tubular section118. First tubular section 114 can have a first end 114 a and a secondend 114 b, second tubular section 116 can have a first end 116 a and asecond end 116 b and/or third tubular section 118 can have a first end118 a and a second end 118 b.

In some embodiments, first end 114 a of first tubular section 114includes connector 114 c that can connect electronics bay 130 to pole110. Connector 114 c can include any connection means known in the art.In some embodiments, second tubular section 116 proceeds coaxially fromsecond end 114 b of first tubular section 114 and/or third tubular 118section tubular section proceeds coaxially from second end 116 b ofsecond section 116. Diameters and lengths of first tubular section 114,second tubular section 116 and/or third tubular section 118 can bepredefined to provide a tapered shape for pole 110. For example, asshown in FIGS. 2A-2E, diameter of second tubular section 116 can besmaller than diameter of first tubular section 114 and/or diameter ofthird tubular section 118 can be smaller than diameter of second tubularsection 116. In some embodiments, first tubular section 114 has diameterof 30 mm and/or length of 177 mm, second tubular section 116 hasdiameter of 26 mm and/or length of 250 mm and/or third tubular section118 has diameter of 20 mm. In some embodiments, pole 110 and/or each oftubular sections 114, 116 and/or 118 include a screw-thread to enhance ascrew motion of VWC sensor 100 during the installation process.

In some embodiments, first end 116 a of second tubular section 116includes connectors 116 c and/or first end 118 a of third tubularsection 118 includes connectors 118 c. Connectors 116 c, 118 c can beprotrusions and/or can be located equally about an outer surface of pole110 (e.g., as shown in FIGS. 2A-2C).

In some embodiments, VWC sensor 100 includes a first VWC probe 120 a anda second VWC probe 120 b. Helical blade 122 a of first VWC probe 120 acan be connected to an outer surface of a cylindrical shell 121 a and/orhelical blade 122 b of second VWC probe 120 b can be connected to anouter surface of a cylindrical shell 121 b. Cylindrical shells 121 a,121 b can have diameters that match the diameters of second and thirdtubular sections 116, 118, respectively. Cylindrical shells 121 a, 121 bcan also include matching connectors 121 a-1, 121 b-1 (e.g., indents asillustrated in FIGS. 2A-2C) that can be connected to connectors 116 c,118 c and can secure first and second VWC probes 120 a, 120 b to pole110.

In some embodiments, tip 112 of VWC sensor 100 has a first end 112 a anda second end 112 b. First end 112 a can have a diameter that match thediameter of second end 118 b of third tubular section 118. First end 112a of tip 112 can also include connectors 112 c (e.g., protrusions asshown in FIGS. 2A-2C) and/or shell 121 b of second VWC probe 120 b caninclude matching connectors 118 d (e.g., indents as shown in FIGS.2A-2C) such that tip 112 can be connected and/or secured to thirdtubular section 118 and/or to shell 121 b of second VWC probe 120 b. Insome embodiments, second end 112 b of tip 112 has a tapered shape thatcan allow for, for example, VWC sensor 100 to penetrate to a target soilduring an installation procedure.

In some embodiments, connectors 112 c, 116 c, 118 c and/or 118 d includecatches know in the art (e.g., detents) that can enhance securing of VWCprobes 120 and tip 112 to pole 110.

The diameter of first VWC probe 120 a that can match the diameter ofsecond tubular section 116, the diameter of second VWC probe 120 b thatcan match the diameter of third tubular section 118 and/or the diameterof first end 112 a of tip 112 that can match the diameter of second end118 b of third tubular section 118 can simplify the assembly of VWCsensor 100, as shown in FIG. 2C. The assembled VWC sensor 100 is shownin FIGS. 2D-2E.

In some embodiments, VWC probe 120 includes three layers: a first layerthat includes helical blade 122, a second layer that includes RFelectrodes 124 secured to a substrate 125, and a third protective layer126 (e.g., as shown in FIGS. 2A-2B). Substrate 125 can be secured tohelical blade 122. Protective layer 126 can cover RF electrodes 124 toprovide a protection during an installation of VWC sensor 100 within atarget soil. In some embodiments, RF electrodes 124 are secured tohelical blade 122 (without substrate 125). In some embodiments, helicalblade 122 of VWC probe 120 completes a helical path of at least 360°around pole 110. In some embodiments, RF electrodes 124 have a helicalshape that corresponds to shape of helical blade 122 and/or complete ahelical path of at least 360° around pole 110.

FIGS. 3A-3B are illustrations of various configurations of a tip 112 ofa volumetric water content (VWC) sensor 100, according to someembodiments of the invention. FIG. 3A presents an isometric view and aside view of a tip 112-1. FIG. 3B present a cross-section view of tip112-2.

In some embodiments, tip 112 includes at least two prongs 112 d, 112 e,where each prong 112 d, 112 e includes RF electrodes 124 (e.g., as shownin FIG. 3A). Each prong 112 d, 112 e can have a helical shape and/or caninclude a nonconductive material. An RF field can be generated by RFelectrodes 124 of each prong 122 d, 122 e to measure a VWC of a targetsoil in a measurement region between the RF electrodes.

In some embodiments, tip 112 has a gap 112 f (e.g., as shown in FIG.3B). Tip 112 can have a tapered end (e.g., tip 112-2 as shown in FIG.3A). Tip 112-2 can include RF electrodes 124 secured to an inner lateralsurface of the tip within gap 112 f.

FIGS. 4A-4D are illustrations of various configurations ofradiofrequency (RF) electrodes 124 of a volumetric water content (VWC)sensor 100, according to some embodiments of the invention. In someembodiments, two VWC probes 120 a, 120 b are positioned adjacently at afirst predefined longitudinal location along pole 110 and/or two VWCprobes 120 c, 120 d are positioned adjacently at a second predefinedlongitudinal location along pole 110 (see e.g., FIG. 4A). RF electrodes124 a, 124 b of adjacent VWC probes 120 a, 120 b and/or RF electrodes124 c, 124 d of adjacent VWC probes 120 c, 120 d can face each other. ARF field can be generated by facing RF electrodes 124 a, 124 b and/orfacing RF electrodes 124 c, 124 d to measure a VWC of a target soil inmeasurement regions between the RF electrodes. A longitudinal distancebetween adjacent VWC probes 120 a, 120 b, a longitudinal distancebetween adjacent VWC probes 120 c, 120 d, the first longitudinallocation and/or the second longitudinal location can be predefined to,for example, optimize the accuracy of moisture measurements of a targetsoil and/or to improve a contact between helical blades 122 a, 122 b,122 c b 122 d and the target soil during a screwing motion of aninstallation process, as described above.

In some embodiments, VWC sensor 100 includes RF electrodes 124-1. RFelectrodes 124-1 can be circular and/or can be secured to an outersurface of pole 110. RF electrodes 124-1 can be surface electrodes. Insome embodiments, RF electrodes 124 a-1, 124 b-1 are positioned betweentwo adjacent VWC probes 120 a, 120 b and/or RF electrodes 124 c-1, 124d-1 are positioned between two adjacent VWC probes 120 c, 120 d atpredefined longitudinal locations (e.g., as shown in FIG. 4B). In someembodiments, RF electrodes 124 a-1, 124 b-1 and/or RF electrodes 124c-1, 124 d-1 are electrical continuations of respective VWC probes 120a, 120 b and/or 120 c, 120 d. In some embodiments, RF electrodes 124-1only are secured to pole 110 (without RF electrodes 124 secured tohelical blades 122). For example, RF electrodes 124-1 a, 124-1 b, 124-1c, 124-1 d as shown in FIG. 4C. In some embodiments, VWC sensor 100includes at least one VWC probe 120 and/or RF electrodes 124-1, whereVWC probe 120 can also include RF electrodes 124, as shown in FIG. 4D.

FIGS. 5A-5E are illustrations of a volumetric water content (VWC) sensor100 including radiofrequency (RF) electrodes 124-2 protruding above atleast one surface of helical blades 122, according to some embodimentsof the invention. FIG. 5A present a side view and an isometric view ofVWC sensor 100 (a left hand-side and a right-hand side, respectively).FIG. 5B presents an isometric blow-up view of VWC probe 120 of VWCsensor 100. FIGS. 5C-5E present a cross-section view of a portion of VWCsensor 100.

In some embodiments, tip 112 of VWC sensor 100 includes a helical blade112 g (e.g., as shown in FIG. 5A). In some embodiments, RF electrode 124is secured to an outer lateral side of helical blade 122 of at least oneVWC probe 120 (e.g., as shown in FIG. 5A). In some embodiments, at leastone RF electrode 124-2 is embedded within helical blade 122 at apredefined radial distance from pole 110 such that embedded RFelectrodes 124-2 protrude above at least one of surfaces of helicalblade 122 (e.g., as shown in FIGS. 5A-5B). RF electrodes 124-2 can bethree-dimensional electrodes and/or can have a helical shape thatcorresponds to shape of helical blade 122. An RF field can be generatedby RF electrodes 124-2 and/or RF electrodes 124 to measure a VWC of atarget soil 80 in a measurement region 140 between the RF electrodes, asschematically illustrated by arrows in FIG. 5C. In some embodiments,helical blade 122 and/or pole 110 occupies less than 10% of measurementregion 140.

In some embodiments, a temperature sensor 128 is embedded within helicalblade 122 of VWC probe 120, as shown in FIGS. 5A-5B. Temperature sensor128 can include a thermal resistor and/or can measure a temperature of atarget soil. The thermal resistor of temperature sensor 128 can be apart of electrical circuitry of electronics unit (e.g., electronics unit160 shown in FIGS. 8-9) and/or can transmit information regarding thetemperature by, for example, changing a DC level of RF signals generatedby RF electrodes 124 and/or RF electrodes 124-2. In some embodiments, aplurality of sensors are embedded and/or secured to helical blades 122of VWC probes 120, for example, a pH sensor, a pressure sensor, asalinity sensor and/or a sensor that can measure level of mineral in atarget soil.

In some embodiments, helical blades 122 include a plurality of holes 126positioned between pole 110 and protruding RF electrodes 124-2 and/or RFelectrodes 124 (e.g., as shown in FIG. 5A-5B). Holes 126 can drain awater 90 flowing along pole 110 and/or along helical blades 122 (e.g.,as indicated by dashed arrows in FIG. 5D) to prevent accommodation ofthe water in a vicinity of RF electrodes 124-2 and/or RF electrodes 124(e.g., as shown in FIG. 5D). In some embodiments, helical blades 122 aresecured to pole 110 at an angle 156 with respect to the pole to providea slope that facilitates drainage of flowing water 90 (e.g., as shown inFIG. 5D).

In some embodiments, pole 110 of VWC sensor 100 has a diameter 157ranging between 10-40 mm (e.g., as shown in FIG. 5E). Helical blades 122can have a diameter of 158 ranging between 80-120 mm. For example,diameter 158 a of helical blade 122 a can be greater than diameter 158 bof helical blade 122 b (e.g., as shown in FIG. 5E) such that helicalblade 122 a, which can follow a screwing path of helical blade 122 bduring a screwing motion of an installation process, enters aundisturbed soil, thereby providing a good contact between helical blade122 a and/or RF electrodes 124-2 a and target soil 80.

In some embodiments, RF electrodes 124-2 (e.g., as shown in FIG. 5A)and/or RF electrodes 124 (e.g., as shown in FIGS. 1B-1C, FIG. 2A-2E,FIG. 4A-4D) positioned at predefined radial distance 154 from pole 110,as described above and schematically shown in FIG. 5E. Radial distance154 can range between 18-40 mm and/or such that RF electrodes 124-2and/or RF electrodes 124 being positioned at 30% most lateral portion ofhelical blades 122 (e.g., RF electrodes 124-2 a, 124-2 b secured tohelical blades 122 a, 122 b as shown in FIG. 5E). Radial distance 154(e.g., radial distance of RF electrodes 124, 124-2 from pole 110) and/ora radial distance 154 a between the RF electrodes (e.g., RF electrodes124-2 a embedded within helical blade 122 a, as shown in FIG. 5E) can bedefined based on a desired RF field to be generated to measure a VWC ofa target soil 80.

In some embodiments, helical blades 122 a, 122 b of VWC probes 120 a,120 b are secured to pole 110 and separated by longitudinal distance 152(e.g., as shown in FIG. 5E). Longitudinal distance 152 can be predefinedto, for example, optimize the accuracy of VWC measurement of a targetsoil 80 and/or to provide a good contact between helical blades 122 a,122 b and the target soil during a screwing motion of an installationprocess.

For example, longitudinal distance 152 can be predefined such thathelical blades 122 a, 122 b follow a same helical path along pole 110 aswould if helical blades 122 a, 122 b being parts of a single helicalblade (e.g., helical blade 110, as shown in FIG. 6). In someembodiments, longitudinal distance 152 has a value of k pitches 159,where k is an integer (e.g., as shown in FIG. 6). In some embodiments, kis greater or equal to 2 (k≥2). Separation of helical blades 122 a, 122b by longitudinal distance 152 can prevent continuous water flow along awhole length of pole 110 and provide at least two zones of target soil80 (e.g., schematically separated by broken line 92 in FIG. 5E) throughwhich water flow is discontinuous. In some embodiments, longitudinaldistance 152 deviates by 2-4% from the value of k pitches 159 such thathelical blade 122 a) such that helical blade 122 a, which can follow ascrewing path of helical blade 122 b during the screwing motion of theinstallation process, enters a undisturbed soil, thereby providing agood contact between helical blade 122 a and/or RF electrodes 124 a anda target soil, which does not follow a same screwing path of helicalblade 122 b during a screwing motion of an installation process, entersa undisturbed soil, thereby improving a contact between helical blade122 a and/or RF electrodes (e.g., RF electrodes 124-2 a as shown in FIG.5E) and target soil 80. These considerations may be applicable to any ofthe configurations of VWC sensors 100, including configurations with acentral shaft (e.g., with pole 110). FIG. 6 further illustratesschematically that the distance between blades, indicated by 159 a maycorrespond exactly or approximately to an integer number of pitches,represented schematically by the broken-line windings.

FIG. 6 is an illustration of configuration of volumetric water content(VWC) sensors 100 a, 100 b with a support 110 being a coreless helicalblade, according to some embodiments of the invention. In someembodiments, coreless helical blade 110 has a tapered shape (e.g., asshown in FIG. 6). VWC sensors 100 a, 100 b can include at least one VWCprobe 120, e.g., VWC probes 120 a, 120 b, as shown in FIG. 6. In someembodiments, VWC probes 120 a, 120 b are positioned concentrically alonga longitudinal axis 155 of coreless helical blade 110 at predefinedlongitudinal locations and/or include RF electrodes 124 a, 124 b. Insome embodiments, VWC probes 120 a, 120 b are VWC probes described inFIGS. 1-5. VWC sensors 100 a, 100 b can include at least one electronicsunit (e.g., electronics unit 160 as shown in FIGS. 8-9). In someembodiments, the electronics units are embedded within coreless helicalblade 110 of VWC sensors 100 a, 100 b.

FIG. 7 is an illustration of a volumetric water content (VWC) probe 120including segmented RF electrodes 124-3, according to some embodimentsof the invention. FIG. 7 presents a top view of VWC probe 120. In someembodiments, RF electrodes of VWC probe 120 (e.g., RF electrodes 124,124-1, and/or 124-2 as shown in FIGS. 1-6) are segmented RF electrodes(e.g., RF electrodes 124-3, as shown in FIG. 7) that are secured and/orembedded within helical blade 122. In some embodiments, VWC probe 120has eight pairs of segmented RF electrodes 124-3 (e.g., pairs 124-3 a .. . 124-3 g as shown in FIG. 7). In some embodiments, an RF field can begenerated and/or measured by segmented RF electrodes 124-3 of each pair.RF fields measured by each pair of RF electrodes 124-3 a . . . 124-3 gcan be averaged to determine a VWC of a target soil. In someembodiments, RF field measured by at least one pair of segmented RFelectrodes, for example, by pair 123-3 c, can significantly differs fromRF fields measured by the rest of the pairs, for example due toaccommodation of air bubbles on RF electrodes of pair 123-3 c.Accordingly, RF field measured by pair 123-3 c can be excluded fromaveraging, thereby eliminating introduction of measurement errors.

One advantage of the present invention can include enabling aself-tapping installation of VWC sensor 100. The self-tappinginstallation can include pushing tapered tip 112 of VWC sensor 100 intoa target soil and/or establishing a rotational motion of the sensorabout its longitudinal axis. The rotational motion of helical blades 122secured along VWC sensor 100 (e.g., as shown in FIG. 1) can generate ascrewing action that can wind the sensor into the target soil, such thatno pre-drilling procedures are required, which minimizes the disturbanceof the soil thereof and reduces vertical flow of water along pole 110and/or helical blades 120.

During an installation of VWC sensor 100, a target soil can be disturbedin a vicinity of pole 110. Disclosed VWC sensor 100 can include RFelectrodes 124 secured to helical blades 122 of VWC probes 120 atpredefined radial distances from pole 110 (e.g., as shown in FIG. 1).Accordingly, another advantage of the present invention is that it canenable alienating the VWC measurement (e.g., by RF electrodes 124) awayfrom pole 110 such that measurements of undisturbed soil are performed.

During an installation of VWC sensor 100, a target soil can also bedisturbed in a vicinity of helical blades 122. Disclosed VWC sensor 100can include RF electrode 124 secured to an outer lateral side of helicalblade 122 and at least one RF electrode 124-2 embedded within the samehelical blade 122 such that embedded RF electrodes 124-2 protrude aboveat least one of surfaces of the blade (e.g., as shown in FIGS. 5A-5B).Accordingly, another advantage of the present invention is that it canenable alienating the VWC measurement (e.g., by lateral RF electrodes124 and protruding RF electrodes 124-2) away from the surfaces ofhelical blades 122 such that it can allow measurement of undisturbedsoil.

FIG. 8 is a schematic block diagram illustrating an electronics unit 160of volumetric water content (VWC) sensor 100, according to someembodiments of the invention. In some embodiments, electronics unit 160can be an enablement to a transmission line based on amplitude domainreflectometry (ADR), time domain reflectometry (TDR), frequency domainreflectometry (FDR) and/or time domain transmission (TDT) electroniccircuits. Electronics unit 160 illustrated in FIGS. 7-8 is an enablementto a transmission line based on ADR electronic circuit as describedbelow. In some embodiments, electronics unit 160 can be an enablement toa capacitance probe.

An RF signal can be generated by a source 161 (e.g., an oscillator). Insome embodiments, the generated RF signal has a frequency of 100 MHz.The generated RF signal can be transmitted to a signal conditioning unit162 (e.g., a filter) to create a filtered RF signal. The filtered RFsignal can be transmitted through a first transmission line 163 (e.g.,phase shifter) and/or through a second transmission line 164 to a targetsoil. In some embodiments, at least a portion of transmission line 164is at least one VWC probe 120 (e.g., as disclosed in FIG. 1, FIGS.2A-2E, FIGS. 4A-4C and/or FIG. 5). In some embodiments, firsttransmission line 163 has an impedance value of Z_(L) and/or secondtransmission line 164 has an impedance value of Z_(P).

The impedance Z_(P) of transmission line 164 can be based on a relativedielectric constant E of the target soil that surrounds transmissionline 164. The relative dielectric constant E can be based on a moisturelevel of the target soil. For example, Equation 1 shows the impedanceZ_(P) of the transmission 164 line as follows:

$\begin{matrix}{Z_{P} \propto \frac{1}{\sqrt{ɛ}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$A reflection coefficient ρ of transmission line 163 and transmissionline 164 can be based on Z_(L), Z_(P). For example, Equation 2 shows thereflection coefficient ρ as follows:

$\begin{matrix}{\rho = \frac{Z_{P} - Z_{L}}{Z_{P} + Z_{L}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$A voltage value V₀ (e.g., the filtered RF signal) at a junction 162 a offilter 162 and transmission line 163 and/or a voltage value V_(P) at ajunction 163 a of transmission line 163 and transmission line 164 can bebased the reflection coefficient ρ. For example, Equation 3 and Equation4 show the voltage value V₀ and the voltage value V_(P) as follows:V₀∝(1−ρ)   (Equation 3)V_(P)∝(1+ρ)   (Equation 4)The voltage value V₀ can also be based on forward voltage value V_(FWD)and reflected voltage value V_(REF). For example, Equation 5 shows thevoltage value V₀ as follows:V ₀ =V _(FWD) +V _(REF)   (Equation 5)The voltage value V₀ and/or the voltage value V_(P) can be measured byrespective RF detectors 165, 166 and transmitted to a differentialamplifier 167 to generate a differential voltage value ΔV=V₀−V_(P). Thedifferential voltage value ΔV can be based on the reflective coefficientρ and as a result can be based on the dielectric constant ε of themoisture level of the target soil, such that allowing determining thevalue of ε. For example, Equation 6 shows the differential voltage valueΔV as follows:ΔV=V ₀ −V _(P)∝2ρ∝ε  (Equation 6)An example of a dependence of differential voltage value ΔV on themoisture level ε of the target soil is illustrated in graph 168.

FIG. 9 is a schematic block diagram of an electronic circuitry ofelectronics unit of volumetric water content (VWC) sensor 100, accordingto some embodiments of the invention. An oscillator 161 can generate aRF signal. The generated RF signal can be filtered by a filter 162 togenerate a filtered RF signal. The filtered RF signal can be transmittedthrough a phase shifter 163 (e.g., that can act as a transmission line)and through a second transmission line 164 to a target soil.

Second transmission line 164 can include a switch 164-1 and/or acontroller 164-2. Controller 164-2 can control switch 164-1 to connectphase shifter 163 to at least one of: a phase shifter 164-3 a, a phaseshifter 164-3 b, a first reference load 164-4 a and/or a secondreference load 164-4 b. In some embodiments, phase shifter 164-3 a isconnected to VWC probe 120 a and/or phase shifter 164-3 b is connectedto VWC probe 120 b, where VWC probes 120 a, 120 b can be VWC probes 120disclosed in FIG. 1, FIGS. 2A-2E, FIGS. 4A-4C and/or FIG. 5. In someembodiments, VWC probes 120 a, 120 b are positioned at opposing endsalong a longitudinal axis of VWC sensor 100, 100 a.

A voltage value V₀ of the filtered RF signal can be measured by a peakdetector 165 at a junction 162 a of filter 162 and phase shifter 163and/or a voltage value V_(P) at a junction 163 a of phase shifter 163and transmission line 164 can be measured by a peak detector 166. Thevoltages values V₀ and V_(P) can be transmitted to a differentialamplifier 167 to generate a differential voltage value ΔV. The voltagevalue V_(P,) and as a result differential voltage value ΔV can be afunction of the level of moisture ε of the target soil, as disclosedabove (e.g., in Equations 1-6).

In some embodiments, phase shifters 164-3 a, 163-3 b rectify phaseshifts that can be caused by a physical distance between junction 163 a(where voltage value V_(P) is measured) and VWC probes 120 a, 120 b. Insome embodiments, reference loads 164-4 a, 164-4 b are used for acalibration of moisture sensor 100.

In some embodiments, the differential voltage value ΔV is digitalized byan analog to digital converter (ADC) 169 and/or transmitted to anexternal system 90 (e.g., cloud network).

FIG. 10 is a flowchart illustrating a method 200 of measuring aundisturbed volumetric water content (VWC), according to someembodiments of the invention. In some embodiments, method 200 can becarried out using VWC sensor 100 described above (e.g., as shown inFIGS. 1-7).

Method 200 can include generating 210 radiofrequency (RF) signals.Method 200 can include transmitting 220 the generated RF signals to theundisturbed soil using RF electrodes, the RF electrodes positionedconcentrically along an axis being parallel to gravitational force atpredefined longitudinal locations and at predefined radial distancesfrom the axis.

In some embodiments, the RF electrodes have a helical shape. In someembodiments, the RF electrodes secured to helical blades, where thehelical blades can be positioned concentrically along the axis at thepredefined longitudinal locations. In some embodiments, the at least oneof the RF electrodes is secured to an outer lateral side of the at leastone of the helical blades. In some embodiments, the at least one of theRF electrodes is embedded within the at least one of the helical bladessuch that the at least one of the embedded RF electrodes protrudes aboveat least one of surfaces of that helical blade.

Method 200 can include measuring 230 the transmitted RF signals by theRF electrodes. Method 200 can include determining 240 the undisturbedVWC based on the measured RF signals.

FIG. 11 is a flowchart illustrating a method 300 of installing a soilsensor assembly, according to some embodiments of the invention. Method300 can include providing 310 a soil sensor assembly including: arotatably anchorable portion to be rotatably anchored in a soil; and atleast one soil sensor mounted onto the rotatably anchorable portion.Method 300 can include rotatably inserting 320 the soil sensor assemblyinto a soil along an anchoring axis, thereby anchoring the soil moisturesensing assembly in the soil.

In some embodiments, the rotatably anchorable portion includes at leastone threading arranged about the anchoring axis, the at least onethreading includes at least one blade portion extending outwardly fromthe anchoring axis, wherein at least one moisture sensor is located onthe at least one of the blade portions, and wherein the rotatablyinserting of the soil sensor assembly into the soil along the anchoringaxis, thereby anchoring the soil sensor assembly in the soil, isoperative to bring the at least one moisture sensor located on the atleast one of the blade portions into a soil moisture sensing engagementwith a portion of the soil which is substantially undisturbed.

FIG. 12A is a graph illustrating volumetric water content (VWC)measurement results being measured by a prior art profile sensor 40,according to the prior art. FIG. 12B is a graph illustrating volumetricwater content (VWC) measurement results being measured by a VWC sensor100, according to some embodiments of the invention.

Typically, following an irrigation event 20, measurements from bottomsensor 42 of prior art profile sensor 40 (e.g., as shown in FIG. 1A) canerroneously show a rise in VWC of a disturbed target soil (e.g., line42-1 as shown in FIG. 12A) that can be similar in timing and amplitude,to measurements of top sensor 41 (e.g., line 41-1 as shown in FIG. 12A).Such measurements can be biased, since water takes time to filtrate downthrough undisturbed soil.

In contrast, the disclosed sensors were found to be sensitive andindicate irrigation events. Following an irrigation event 20, the VWCmeasurements generated by the VWC sensor 100 clearly show delay intiming between measurement of top sensor 120 a (e.g., line 120 a-1 asshown in FIG. 12B) and measurement of bottom sensor 120 b (e.g., line120 b-1 as shown in FIG. 12B), which emphasizes that a target soil isundisturbed during an installation of VWC sensor 100.

In the following description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will also be apparent to one skilledin the art that the present invention may be practiced without thespecific details presented herein. Furthermore, well known features mayhave been omitted or simplified in order not to obscure the presentinvention. With specific reference to the drawings, it is stressed thatthe particulars shown are by way of example and for purposes ofillustrative discussion of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

Before at least one embodiment of the invention is explained in detail,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is applicable to other embodiments that may bepracticed or carried out in various ways as well as to combinations ofthe disclosed embodiments. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing”, “computing”,“calculating”, “determining”, “enhancing” or the like, refer to theaction and/or processes of a computer or computing system, or similarelectronic computing device, that manipulates and/or transforms datarepresented as physical, such as electronic, quantities within thecomputing system's registers and/or memories into other data similarlyrepresented as physical quantities within the computing system'smemories, registers or other such information storage, transmission ordisplay devices.

In the above description, an embodiment is an example or implementationof the invention. The various appearances of “one embodiment”, “anembodiment”, “certain embodiments” or “some embodiments” do notnecessarily all refer to the same embodiments. Although various featuresof the invention may be described in the context of a single embodiment,the features may also be provided separately or in any suitablecombination. Conversely, although the invention may be described hereinin the context of separate embodiments for clarity, the invention mayalso be implemented in a single embodiment. Certain embodiments of theinvention may include features from different embodiments disclosedabove, and certain embodiments may incorporate elements from otherembodiments disclosed above. The disclosure of elements of the inventionin the context of a specific embodiment is not to be taken as limitingtheir use in the specific embodiment alone. Furthermore, it is to beunderstood that the invention can be carried out or practiced in variousways and that the invention can be implemented in certain embodimentsother than the ones outlined in the description above.

The invention is not limited to those diagrams or to the correspondingdescriptions. For example, flow need not move through each illustratedbox or state, or in exactly the same order as illustrated and described.Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined. While the invention hasbeen described with respect to a limited number of embodiments, theseshould not be construed as limitations on the scope of the invention,but rather as exemplifications of some of the preferred embodiments.Other possible variations, modifications, and applications are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

The invention claimed is:
 1. A volumetric water content (VWC) sensorcomprising: a support configured to secure a position of the VWC sensorin target soil, wherein the support includes a tip; at least oneelectronics unit; at least one helical blade secured along its innerlateral side to an outer surface of the support; and at least one VWCprobe positioned along the support between at least one of the at leastone helical blade and the tip of the support, wherein the at least oneVWC probe includes at least two radiofrequency (RF) electrodes extendingaround the outer surface of the support, wherein the at least one VWCsensor is configured to measure a VWC of a target soil in a measurementregion between the at least two RF electrodes.
 2. The VWC sensor ofclaim 1, wherein the helical blade includes an RF electrode.
 3. The VWCsensor of claim 1, wherein the at least one helical blade includes atleast two helical blades, and wherein the at least one VWC probe ispositioned between two adjacent ones of the at least helical blades. 4.The VWC sensor of claim 1, wherein the at least one VWC probe ispositioned between one of the at least one helical blade and the tip. 5.The VWC sensor of claim 1, wherein each of the at least two RFelectrodes is circular.
 6. The VWC sensor of claim 1, wherein the atleast one electronics unit is embedded within the at least one helicalblade.
 7. The VWC sensor of claim 1, further comprising a protectivelayer covering at least one of the at least two RF electrodes.
 8. Amethod of measuring volumetric water content, the method comprising:providing a volumetric eater content (“VWC”) sensor including: a supportconfigured to secure a position of the VWC sensor in soil, wherein thesupport includes a tip; at least one electronics unit; at least onehelical blade secured along its inner lateral side to an outer surfaceof the support; and at least one VWC probe positioned along the supportbetween at least one of the at least one helical blade and the tip ofthe support, wherein the at least one VWC probe includes at least tworadiofrequency (RF) electrodes extending around the outer surface of thesupport, positioning the VWC sensor in target soil; generating radiofrequency signals by the at least one electronics unit; transmitting thegenerated RF signals to the target soil using the at least two RFelectrodes, receiving the generated RF signals by the at least two RFelectrodes; and determining the VWC based on the received RF signals. 9.The method of claim 8, wherein the at least one helical blade includesat least two helical blades, and wherein the at least one VWC probe ispositioned between two adjacent ones of the at least two helical blades.10. The method of claim 8, wherein the at least one VWC probe ispositioned between one of the at least one helical blade and the tip.11. The method of claim 8, wherein each of the at least two RFelectrodes is circular.
 12. The method of claim 8, wherein the at leastone electronics unit is embedded within the at least one helical blade.13. The method of claim 8, wherein the VWC sensor further comprises aprotective layer covering at least one of the at least two RFelectrodes.